A conventional mechanical machining apparatus comprises a controller and a server driver. The controller controls the server driver to perform a machining process. However, after a period of time of use, the machining apparatus will experience mechanical wear which decreases machining precision. Therefore, machine calibration is normally performed before the machining process to assure that the precision of the processed workpiece is conformed to the requirement of precision after the machining process. In a conventional calibration method, a mechanical calibration module is added to the machining apparatus. However, the added mechanical module requires extra time for assembly and calibration, making the calibration procedure even more inefficient.